Radon (²²²Rn) has been highlighted by a number of authors as a significant public health concern. For example, it is the second most significant cause of lung cancer after tobacco smoking (c. 1000–2000 and 21 000 deaths per year in the UK and USA, respectively), yet a very high proportion of the general public appears to be unaware of the risk. This chapter deals with topical radon issues, such as: radon in the workplace; radon in homes; exposure to radon during leisure activities; radon and water; measurement and monitoring; seasonal correction; remediation; cancer risks; cost–benefit analysis...